The Primary Structure of the Porcine Pancreatic Secretory Trypsin Inhibitor I: AMINO ACID SEQUENCE OF THE REDUCED S-AMINOETHYLATED PROTEIN

Abstract

Abstract The amino acid sequence of porcine pancreatic secretory trypsin inhibitor I (Greene, L. J., Dicarlo, J. J., Sussman, A. J., Bartelt, D. C., and Roark, D. E., J. Biol. Chem., 243, 1804 (1968)) was determined by a combination of selective trypsin and chymotrypsin hydrolysis reactions and conventional methods for sequence determination of small peptides. Arginine-directed cleavage was achieved by blocking lysyl and S-2-aminoethylcysteinyl residues with maleic anhydride. Hydrolysis of lysyl bonds in peptides containing S-2-aminoethylcysteine was accomplished by trypsin at pH 11.0. All of the overlap information required to order the small peptides was obtained by the identification of the amino- and carboxy-terminal residues of the products at each stage of the degradative procedure. The yields of the peptides, 38 to 93%, compared favorably with those obtained by the conventional complete trypsin hydrolysis of the bovine pancreatic secretory trypsin inhibitor, a molecule of the same size and similar structure. The amino acid sequence of the porcine inhibitor has been shown to be [see PDF for sequence]. This sequence exhibits 12 differences in 56 amino acid residues per molecule from that of the bovine pancreatic secretory trypsin inhibitor (Greene, L. J., and Bartelt, D. C., J. Biol. Chem., 244, 2646 (1969)).